Glass fibers are useful in a variety of technologies. For example, glass fibers are commonly used as reinforcements in polymer matrices to form glass fiber reinforced plastics or composites. Glass fibers have been used in the form of continuous or chopped filaments, strands, rovings, woven fabrics, non-woven fabrics, meshes, and scrims to reinforce polymers. In forming glass fibers, a glass forming material is heated in a glass melting furnace until the glass forming material is degraded to a molten state. The molten glass is passed through a bushing block and a bushing, where it is formed into glass filaments. As shown in FIG. 1, a bushing 10 includes a generally rectilinear shaped sidewall 12 and an outwardly extending flange 14 disposed at the upper portion thereof. The flange 14 is adapted to be secured to a supply of molten glass, such as from a bushing block 16. Bushings 10 are generally electrically heated. In this regard, diametrically disposed terminals or ears 18 are attached to a power source (not shown) to conduct current through the bushing 10, including its sidewalls 12 and bottom plate 19. The bottom plate 19 includes orifices or feeder tips 15 which are in fluid communication with the molten glass. The molten glass is attenuated or otherwise pulled from the tips 15 of the bushing 10 to form glass filaments 22. These glass fibers 22 are coated with a sizing composition, such as by the sizing applicator 24. The sized glass fibers 25 are gathered by a gathering shoe 26 into a glass strand 28. The glass strands may be wound into a package 30.
It is known in the art to use a cooling tube 32, as illustrated in FIG. 2, mounted below the flange 14 to “freeze” the molten glass material and form a seal with the bushing block 16. During operation, water flows through the cooling tube 32 to carry away heat absorbed by the cooling tube 32 and create a cold area that has a temperature that is lower than the temperature at which the molten glass solidifies. When the molten glass reaches the area near the cooling tube 32, it becomes a solid and prevents further flow of the glass material, thereby preventing any molten glass leakage from the bushing 10 or bushing block 16.
Typically, the bushing 10 and flange 14 are formed of a precious metal or a precious metal alloy formed of platinum, rhodium, or palladium. Precious metals have been used to form these components because they can withstand the extreme heat associated with the molten glass. However, precious metals are very expensive and tie up millions of dollars of capital investment. Thus, there exists a need in the art to for a glass forming apparatus that reduces costs associated with the formation of glass fibers.